DC switched mode power supplies (SMPS) are used to convert the supply voltage of a circuit into a different DC voltage level. The output voltage of the DC-DC converter may be lower than the input voltage (for example in the case of a buck converter), it may be higher than the input voltage (for example in the case of a boost converter) or it may be either higher or lower (for example in the case of a buck-boost converter). Such circuits comprise a switching transistor, and the output voltage of these circuits is controlled by the duty cycle of the switching transistor.
In order to regulate the duty cycle of the switching transistor, and thus the output voltage, both analogue and digital control circuits have been proposed. Digital control circuits have the advantage over analogue control circuits of using less chip surface area, and are thus the preferred solution in many applications such as laptops, mobile phones, digital cameras etc.
A problem with known digital control circuits is that they are generally inefficient in terms of their power consumption.